SEOUL - North Korea on Saturday threatened a "sacred war" over US-South Korean joint military drills next week as a US envoy urged Pyongyang's new leadership to engage in dialogue with the outside world. The North's National Defence Commission (NDC) denounced the annual joint exercises as a "silent declaration of war," describing them as "unpardonable war hysteria." Key Resolve, a computerised command post exercise, will start on Monday and continue until March 9. Separately, the joint air, ground and naval field training exercise Foal Eagle will be held from March 1 to April 30.